Perfect in-plane ${\mathrm{CrI}}_3$ spin-valve driven by photogalvanic effect

Out-of-plane spin tunneling through the two-dimensional (2D) van der Waals ${\mathrm{CrI}}_3$ multilayer has recently been deeply explored, and giant magnetoresistance has been achieved in various ${\mathrm{CrI}}_3$ magnetic tunneling junctions (MTJs) via the control of interlayer antiferromagnetic coupling by both magnetic and electric fields. In contrast, knowledge of the in-plane spin-transport properties of 2D ${\mathrm{CrI}}_3$ is currently very limited. Here, based on quantum transport simulations, we study the in-plane transport properties of the photocurrent in a ${\mathrm{CrI}}_3$ MTJ with a bilayer/monolayer/bilayer configuration. The photogalvanic effect (PGE) is induced under vertical illumination of elliptically polarized light, giving rise to a robust photocurrent in a broad visible range at zero bias. A perfect spin-valve effect can be achieved with a magnetoresistance of 100% for some photon energies with an appropriate light helicity. Moreover, the PGE photocurrent for the antiparallel configuration is enhanced, as compared to the parallel configuration due to the increased device asymmetry. Our results show that a PGE-driven ${\mathrm{CrI}}_3$ photodetector is a promising candidate for low-power 2D spintronic devices.

Figure 1

(a) Top and (b) side views of the MTJ model. The blue and red spheres represent Cr and I atoms, respectively. Shadows indicate the area illuminated vertically by circularly polarized light propagating along the $x$ direction. (c) and (d) depict spin configurations of the MTJ for the parallel configuration (PC) and antiparallel configuration (APC) for the in-plane AFM state, and (e) and (f) are for the out-of-plane AFM states.

Figure 2

The photocurrent ($J$) for photon energies of 1.6, 1.9, and 2.1 eV in the (a) In_PC and (b) In_APC. (c) The maximum photocurrent $J_{\text{max}}$ for different photon energies. (d) The increase ratio of the photocurrent ($R_J$) and device asymmetry ($R_A$) for the APC with respect to the PC. (e) The device asymmetry $A$ for the APC and PC.

Figure 3

(a) The variation of the MR with the light helicity ($\varphi$) for photon energies of 1.5, 1.6, and 1.9 eV for a MTJ with an in-plane AFM state. (b) The photocurrent varying with $\varphi$ for a photon energy of 1.5 eV, and (c) the maximum MR for different photon energies.

Figure 4

(a) The maximum photocurrent ($J_{\text{max}}$) of different photon energies for MTJs with out-of-plane AFM states. (b) is the increase ratio of the photocurrent $R_J$ and of the device asymmetry $R_A$. (c) is the maximum MR at different photon energies.

Figure 5

(a) The schematic diagram of the asymmetric energy bands for a 2L/1L/2L-${\mathrm{CrI}}_3$ junction, (b) the electronic band structure of bilayer ${\mathrm{CrI}}_3$ with an out-of-plane antiferromagnetic state, and (c) the electric potential for the center region of the device along the diagonal direction and $x$ direction.